The ability to successfully acquire external research funding is an essential skill biomedical research trainees must acquire to make the career transition into independent investigator. During the first 4 years of the National Research Mentoring Network (NRMN), 4 different grant writing coaching group models for biomedical junior faculty and postdoctoral fellows, known to be effective on a small scale, were piloted at a national level. All of the models had an initial in-person training session, followed by virtual coaching meetings (group and/or individual) for several months. Coaching was provided by accomplished investigators with high levels of expertise in NIH proposal writing. However, the models differed in several of their core design features such as trainee eligibility (readiness to write, extent of mentorship in their research area), longevity (4-12 months), type of feedback provided (written, oral, both), proposal sections covered, and use of mock review. These differences enabled comparison of initial outcome and process data across the variations. A total 541 individuals from 156 institutions participated, with 63% from underrepresented groups. Irrespective of model, the great majority of coaching group participants reported meaningful learning gains in their knowledge, skills, and grant writing self-efficacy. Proposal funding outcomes were also positive, but varied between models from 12% to 24% of those submitted. Starting from the model that was most successful and most expandable, and drawing on effective elements of the other models, an enhanced grant writing coaching group model has been designed and is ready to be tested using a randomized controlled trial design. Key variables to be studied are: 1) the `dose' of the writing groups (i.e. a single 5-month intensive process vs. continuing support after the group) and 2) degree of engagement of local scientific mentors during the group (i.e. structured vs. unstructured). A 2 X 2 factor design will involve 288 junior faculty over the 5 years, achieving 2 Specific Aims: Aim 1 - Determine the effectiveness of a new, enhanced coaching intervention on proposal submission and funding rates when varying coaching dose (regular vs. extended), and mode of engaging local mentors with the coaching group (unstructured vs. structured). Aim 2 - Identify individual (person), coaching group, and institution factors that predict submission, resubmission, and funding of proposals. Aim 2 will be achieved by a first-ever in-depth mixed methods research design to determine the mechanisms by which the intervention works. It will combine association analyses with multiple potential predictor variable with in-depth qualitative analysis of person-by- person experiences working toward proposal submission and through review outcomes. The Impact of this study will be a detailed objective analysis of a very promising methodology for assisting junior faculty on the cusp of independence obtain funding. The in-depth study of factors important to and associated with successful funding will enable final refinement of the intervention for broad dissemination and application.